Strahlentherapie und Onkologie

, Volume 194, Issue 1, pp 50–59 | Cite as

Air–electron stream interactions during magnetic resonance IGRT

Skin irradiation outside the treatment field during accelerated partial breast irradiation
  • Jong Min Park
  • Kyung Hwan ShinEmail author
  • Jung-in Kim
  • So-Yeon Park
  • Seung Hyuck Jeon
  • Noorie Choi
  • Jin Ho Kim
  • Hong-Gyun Wu
Original Article



To investigate and to prevent irradiation outside the treatment field caused by an electron stream in the air generated by the magnetic field during magnetic resonance image-guided accelerated partial breast irradiation (APBI).

Materials and methods

In all, 20 patients who received APBI with a magnetic resonance image-guided radiation therapy (MR-IGRT) system were prospectively studied. The prescription dose was 38.5 Gy in 10 fractions of 3.85 Gy and delivered with a tri-cobalt system (the ViewRay system). For each patient, primary plans were delivered for the first five fractions and modified plans with different gantry angles from those of the primary plan (in-treatment plans) were delivered for the remaining five fractions to reduce the skin dose. A 1 cm thick bolus was placed in front of the patient’s jaw, ipsilateral shoulder, and arm to shield them from the electron stream. Radiochromic EBT3 films were attached to the front (towards the breast) and back (towards the head) of the bolus during treatment. Correlations between the measured values and the tumor locations, treatment times, and tumor sizes were investigated.


For a single fraction delivery, the average areas of the measured isodoses of 14% (0.54 Gy), 12% (0.46 Gy), and 10% (0.39 Gy) at the front of the boluses were as large as 3, 10.4, and 21.4 cm2, respectively, whereas no significant dose could be measured at the back of the boluses. Statistically significant but weak correlations were observed between the measured values and the treatment times.


During radiotherapy for breast cancer with an MR-IGRT system, the patient must be shielded from electron streams in the air generated by the interaction of the magnetic field with the beams of the three-cobalt treatment unit to avoid unwanted irradiation of the skin outside the treatment field.


Magnetic field Magnetic resonance image-guided radiation therapy Out-of-field exposure Radiation protection Organs at risk 

Luft-Elektronenstrahl-Interaktionen in der Magnetresonanztomographie-geführten IGRT

Hautbestrahlung außerhalb des Zielgebiets während einer akzelerierten Teilbrustbestrahlung



Beim Einsatz eines Magnetresonanztomographie(MRT)-geführten Bestrahlungsgeräts kann durch die Wechselwirkung von Magnetfeld und Strahlenquelle unerwünscht ein Elektronenstrahl außerhalb der Therapiefelder entstehen. In dieser Studie wurde für akzelerierte Teilbrustbestrahlungen (APBI) diese Strahlung abgeschirmt und näher untersucht.

Arbeitsmittel und Verfahren

Für diese Studie wurden prospektiv 20 Patientinnen ausgewählt, die eine APBI mit einer MRT-geführten Strahlentherapie (MR-IGRT) erhielten. Die Bestrahlung erfolgte mit einem Tri-Kobalt-System, das mit einem Magnetresonanztomographen kombiniert war (ViewRay). Es wurden jeweils 10 Fraktionen mit einer Einzeldosis von 3,85 Gy und der resultierenden Gesamtdosis von 38,5 Gy appliziert. Zur Reduktion der Hautdosis wurden pro Patientin 2 unterschiedliche Therapiepläne für jeweils 5 Fraktionen mit unterschiedlichen Tragarmwinkeln eingesetzt. Zur Abschirmung des unerwünschten Elektronenstrahls außerhalb der Strahlenfelder wurde ein 1 cm starker Bolus vor dem Kiefer sowie vor der ipsilateralen Schulter und dem Arm der Patientin positioniert. Vor dem Bolusmaterial (Richtung Brust) und hinter dem Bolusmaterial (Richtung Kopf) wurden EBT3-Radiochromröntgenfilme befestigt, um die ein- und austretende Dosis zu messen. Die Abhängigkeiten der Messwerte von der Lokalisation des bestrahlten Tumors, der Bestrahlungszeit und der Tumorgröße wurden untersucht.


Für jeweils eine Strahlenfraktion wurden auf den Röntgenfilmen vor dem Bolusmaterial (Richtung Brust) die von den einzelnen Isodosen eingeschlossenen Flächen vermessen: die 14 %-Isodosis (0,54 Gy) umschloss im Mittel eine Fläche von 3,6 cm2, die 12 %-Isodosis (0,46 Gy) im Mittel 10,4 cm2 und die 10 %-Isodosis (0,39 Gy) im Mittel 21,4 cm2. Die Röntgenfilme hinter dem Bolusmaterial zeigten hingegen keine signifikante Dosisbelastung an. Statistisch signifikante, aber nur geringe Korrelationen wurden zwischen der Dosisbelastung und den Behandlungszeiten beobachtet.


Werden Brustkrebspatientinnen mit einem MRT-geführten Tri-Kobalt-Bestrahlungsgerät behandelt, kann durch eine Wechselwirkung von Strahlenquelle und Magnetresonanztomograph ein Elektronenstrahl außerhalb der Therapiefelder unerwünscht entstehen. Dieser muss zur Schonung der Haut berücksichtigt und abgeschirmt werden.


Magnetfeld Magnetresonanztomographie-geführte Strahlentherapie Strahlenbelastung außerhalb der Therapiefelder Strahlenschutz Risikoorgane 



This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIP) (No. 2015R1C1A1A01054192).

Compliance with ethical guidelines

Conflict of interest

J.M. Park, K.H. Shin, J.-i. Kim, S.-Y. Park, S.H. Jeon, N. Choi, J.H. Kim and H.-G. Wu declare that they have no competing interests.

Ethical standards

This study was approved by the institutional review board of Seoul National University College of Medicine/Seoul National University Hospital (IRB No. 1610-083-799).


  1. 1.
    Correa C, Harris EE, Leonardi MC et al (2017) Accelerated Partial Breast Irradiation: Executive summary for the update of an ASTRO Evidence-Based Consensus Statement. Pract Radiat Oncol 7:73–79CrossRefPubMedGoogle Scholar
  2. 2.
    Smith BD, Arthur DW, Buchholz TA et al (2009) Accelerated partial breast irradiation consensus statement from the American Society for Radiation Oncology (ASTRO). Int J Radiat Oncol Biol Phys 74:987–1001CrossRefPubMedGoogle Scholar
  3. 3.
    Polgar C, Van Limbergen E, Potter R et al (2009) Patient selection for accelerated partial-breast irradiation (APBI) after breast-conserving surgery: recommendations of the Groupe Europeen de Curietherapie-European Society for Therapeutic Radiology and Oncology (GEC-ESTRO) breast cancer working group based on clinical evidence. Radiother Oncol 94:264–273CrossRefGoogle Scholar
  4. 4.
    Chang JH, Lee NK, Kim JY et al (2013) Phase II trial of proton beam accelerated partial breast irradiation in breast cancer. Radiother Oncol 108:209–214CrossRefPubMedGoogle Scholar
  5. 5.
    Sayan M, Wilson K, Nelson C, Gagne H (2017) Rubin D Heimann R. A novel schedule of accelerated partial breast radiation using intensity-modulated radiation therapy in elderly patients: survival and toxicity analysis of a prospective clinical trial. Radiat Oncol J 35:32–38CrossRefPubMedPubMedCentralGoogle Scholar
  6. 6.
    Sung K, Lee KC, Lee SH (2014) Ahn SH Choi J. Cardiac dose reduction with breathing adapted radiotherapy using self respiration monitoring system for left-sided breast cancer. Radiat Oncol J 32:84–94CrossRefPubMedPubMedCentralGoogle Scholar
  7. 7.
    Vicini FA, Chen P, Wallace M et al (2007) Interim cosmetic results and toxicity using 3D conformal external beam radiotherapy to deliver accelerated partial breast irradiation in patients with early-stage breast cancer treated with breast-conserving therapy. Int J Radiat Oncol Biol Phys 69:1124–1130CrossRefPubMedGoogle Scholar
  8. 8.
    Rusthoven KE, Carter DL, Howell K et al (2008) Accelerated partial-breast intensity-modulated radiotherapy results in improved dose distribution when compared with three-dimensional treatment-planning techniques. Int J Radiat Oncol Biol Phys 70:296–302CrossRefPubMedGoogle Scholar
  9. 9.
    Oliver M, Chen J, Wong E, Van Dyk J, Perera F (2007) A treatment planning study comparing whole breast radiation therapy against conformal, IMRT and tomotherapy for accelerated partial breast irradiation. Radiother Oncol 82:317–323CrossRefPubMedGoogle Scholar
  10. 10.
    Park CK, Pritz J, Zhang GG, Forster KM, Harris EE (2012) Validating fiducial markers for image-guided radiation therapy for accelerated partial breast irradiation in early-stage breast cancer. Int J Radiat Oncol Biol Phys 82:e425–e431CrossRefPubMedGoogle Scholar
  11. 11.
    Wooten HO, Green O, Yang M et al (2015) Quality of Intensity Modulated Radiation Therapy Treatment Plans Using a (6)(0)Co Magnetic Resonance Image Guidance Radiation Therapy System. Int J Radiat Oncol Biol Phys 92:771–778CrossRefPubMedGoogle Scholar
  12. 12.
    Wooten HO, Rodriguez V, Green O et al (2015) Benchmark IMRT evaluation of a Co-60 MRI-guided radiation therapy system. Radiother Oncol 114:402–405CrossRefPubMedGoogle Scholar
  13. 13.
    Park JM, Park S, Wu H, Kim J (2015) Commissioning experience of tri-cobalt-60 MRI-guided radiation therapy system. Prog Med Phys 26:193–200CrossRefGoogle Scholar
  14. 14.
    Mutic S, Dempsey JF (2014) The ViewRay system: magnetic resonance-guided and controlled radiotherapy. Semin Radiat Oncol 24:196–199CrossRefPubMedGoogle Scholar
  15. 15.
    Kim J, Park S, Lee YH, Shin KH, Wu H, Park JM (2015) Effect of low magnetic field on dose distribution in the partial-breast irradiation. Prog Med Phys 26:208–214CrossRefGoogle Scholar
  16. 16.
    Vicini F, White J, Arthur D, et al (2011) NSABP B‑39/RTOG 0413: A randomized phase III study of conventional whole breast irradiation versus partial breast irradiation for women with stage 0, I, or II breast cancer. Available at: Accessed 6 February 2016
  17. 17.
    Kim JI, Park SY, Kim HJ, Kim JH, Ye SJ, Park JM (2014) The sensitivity of gamma-index method to the positioning errors of high-definition MLC in patient-specific VMAT QA for SBRT. Radiat Oncol 9:167CrossRefPubMedPubMedCentralGoogle Scholar
  18. 18.
    Reyhan ML, Chen T, Zhang M (2015) Characterization of the effect of MRI on Gafchromic film dosimetry. J Appl Clin Med Phys 16:5743CrossRefGoogle Scholar
  19. 19.
    Micke A, Lewis DF, Yu X (2011) Multichannel film dosimetry with nonuniformity correction. Med Phys 38:2523–2534CrossRefPubMedGoogle Scholar
  20. 20.
    Ferreira BC, Lopes MC, Capela M (2009) Evaluation of an Epson flatbed scanner to read Gafchromic EBT films for radiation dosimetry. Phys Med Biol 54:1073–1085CrossRefPubMedGoogle Scholar
  21. 21.
    Lewis D, Chan MF (2015) Correcting lateral response artifacts from flatbed scanners for radiochromic film dosimetry. Med Phys 42:416–429CrossRefPubMedGoogle Scholar
  22. 22.
    ICRP (2007) The 2007 Recommendations of the International Commission on Radiological Protection. ICRP Publication 103. Ann. ICRP 37(2–4)Google Scholar

Copyright information

© Springer-Verlag GmbH Deutschland 2017

Authors and Affiliations

  • Jong Min Park
    • 1
    • 2
    • 3
    • 4
  • Kyung Hwan Shin
    • 1
    • 2
    • 3
    • 5
    Email author
  • Jung-in Kim
    • 1
    • 2
    • 3
  • So-Yeon Park
    • 1
    • 2
    • 3
  • Seung Hyuck Jeon
    • 1
  • Noorie Choi
    • 5
  • Jin Ho Kim
    • 1
    • 2
    • 3
  • Hong-Gyun Wu
    • 1
    • 2
    • 3
    • 5
  1. 1.Department of Radiation OncologySeoul National University HospitalSeoulKorea (Republic of)
  2. 2.Biomedical Research InstituteSeoul National University HospitalSeoulKorea (Republic of)
  3. 3.Institute of Radiation MedicineSeoul National University Medical Research CenterSeoulKorea (Republic of)
  4. 4.Robotics Research Laboratory for Extreme EnvironmentsAdvanced Institutes of Convergence TechnologySuwonKorea (Republic of)
  5. 5.Department of Radiation OncologySeoul National University College of MedicineSeoulKorea (Republic of)

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